[GHC] #7635: SafeHaskell implying other options

[GHC]

#7635: SafeHaskell implying other options
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Reporter:  shachaf                      |          Owner:                  
    Type:  feature request              |         Status:  new             
Priority:  normal                       |      Component:  Compiler        
 Version:  7.6.1                        |       Keywords:                  
      Os:  Unknown/Multiple             |   Architecture:  Unknown/Multiple
 Failure:  GHC accepts invalid program  |      Blockedby:                  
Blocking:                               |        Related:                  
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 There have been several type checker bugs -- including #7453 and #7354 --
 that have led to type-checker unsafeCoerce/panic/etc., which is a problem
 under SafeHaskell. In many cases the issue is caught by `-dcore-lint`. I'm
 not sure how much overhead core-linting has, but it seems like it could be
 a good idea to turn it on by default at least when SafeHaskell is on.

 Right now it's listed as a "compiler debugging option", but it seems that
 common wisdom is that you should use it if you care about security. Should
 you also use `stg-lint`/`cmm-lint`? Any other options? This should be
 clearly documented.

 Relatedly: Earlier today someone was running a Haskell-evaluating IRC bot.
 It was running with SafeHaskell, but also happened to have
 GeneralizedNewtypeDeriving turned on, which made it possible to derive
 `unsafeCoerce`. Should more care be taken that unsafe options are never
 turned on at the same time as SafeHaskell?

 (Continued from #7354.)

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7635>
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